In recent years, conductive diamond-like carbon (DLC) has been used for probes for measuring electric properties of semiconductors and various kinds of electronic component materials. Previously used were probes in which a base material made of beryllium copper was plated with gold, but such probes had the following problems.
1) During the measurement of electrical properties of semiconductors or electronic components, the solder on the electrodes thereof is brought into repeated contact with a probe and adheres to the surface of the probe, changing the contact resistance. Consequently, inspection results vary and therefore stable quality cannot be ensured.
2) Abrasion resistance of the base material for probes is insufficient and therefore frequent probe replacement is required. Consequently, frequent gold plating is also required, which results in higher costs, and the time required for probe replacement results in a decreased productivity.
To solve the above problems, conductive DLC was developed, and prevention of solder debris and improvement of abrasion resistance have been pursued (e.g. see Patent Literature 1 and Patent Literature 2).
Solder debris on the surface of probes is mainly associated with the surface free energy of materials thereof. Use of an organic carbon film instead of gold can reduce the surface free energy and as a result reduces the possibility of solder adhesion to the surface of probes.
Meanwhile, it is not easy to achieve both hardness and conductivity. To make a carbon film harder, cubic diamond component in the carbon film needs to be increased. However, carbon containing increased diamond component exhibits insulation. To improve conductivity, graphite component in the carbon film needs to be increased. However, a carbon film containing increased graphite component is extremely soft (since the hardness of graphite is 0.1 GPa or less). Thus, hardness and conductivity are not compatible, and therefore it is not easy to achieve both hardness and conductivity.
Hence, thin films having conductivity and a certain level of hardness due to impurities, such as boron, doped in DLC have been applied in the above technical field (e.g. see Patent Literature 3). Conductive DLC films currently used as coated films of probes have hardness in the range of 9 to 30 GPa and volume resistivity in the range of 1×10−4 to 1×102 Ω·cm.
However, due to miniaturization of components and increase in the speed of production lines in the process of manufacturing semiconductors and electronic components, DLC films are currently required to have the following properties: 1) higher hardness (abrasion resistance) and not higher volume resistivity than those of existing conductive DLC films; and 2) stability in terms of volume resistivity and hardness even in a high temperature range around 200° C.